If you demand nothing but Castrol TWS for your high performance E39 M5 engine, then we have good news. Now you can buy Castrol Edge Professional TWS--for less. This is the same oil specified by BMW engineers for the M5. The same oil that came in your beast as it breached Bavaria. Not a similar oil; not a substitute. The real deal. The difference? The bottle (and the price). Save on your next oil change by buying Castrol TWS in a slightly different bottle, and put the savings in the bank. Or the tank.